1. Technical Field
The present invention pertains generally to vehicle sunroof systems and more particularly, to vehicle sunroof systems which attenuate wind noise transmitted into the vehicle passenger compartment while the vehicle is operated and the sunroof is in an open condition.
2. Discussion
It has become commonplace to employ sunroof assemblies in automotive vehicle roof systems. Such sunroof assemblies offer sunlight access through a fixed vehicle roof opening when a sunroof panel is disposed in either an open or closed position, and an opaque sunshade is openly slid. Furthermore, open air motoring access is provided through a sun roof aperture when the sunroof panel is fully opened, thereby increasing ventilation within the passenger compartment.
Most conventional sunroof assemblies have a sunroof tub, an electric motor, a cable driven drive mechanism and a sunroof panel. A driver accessible switch is also typically provided for selectively energizing and de-energizing the electric motor in a manual manner. These conventional sunroof assemblies move the sunroof panel between a fully closed position generally flush with the exterior of the vehicle roof and a fully open position either stowed below or above the stationary vehicle roof.
Many conventional sunroof assemblies have problems with noise that is transmitted into the vehicle passenger compartment which results from the flow of air proximate the sunroof aperture. One component of the wind noise typically results from wind buffeting and is generally characterized by low frequencies. Another component of the wind noise typically results from wind rushing over the vehicle trim and other vehicle components (e.g., antenna) and is generally characterized by high frequencies.
In an effort to attenuate the low frequency portion of the wind noise, air dams have frequently been incorporated into sunroof assemblies. These air dams generally pivot from a retracted position when the sunroof panel is into and an extended position when the sunroof panel is opened. Various air dam constructions have been suggested or employed to affect the low-frequency portion of wind noise and/or to improve air flow into the passenger compartment. While air dams have been employed with some success in attenuating low-frequency noise in certain situations, several drawbacks have been noted.
One drawback relates to the positioning of the air dam at the fully extended position regardless of the speed of the vehicle or the amount that sunroof panel is open. It is well known in the art that both of these factors greatly influence the magnitude of the low-frequency portion of the wind noise, yet these systems do not adjust the position of the air dam between the retracted and extended positions to optimize performance of the air dam. Furthermore, these air dams are typically constructed with little regard to substantially attenuate the high-frequency portion of the wind noise.
Other efforts in this area have focused on variable positioning of the sunroof panel as the vehicle speed changes. While this strategy has greatly attenuated the magnitude of the low-frequency portion of the wind noise, this strategy does not substantially attenuate the magnitude of the high-frequency portion of wind noise.